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I'm having a heck of a time building this notch filter

Discussion in 'Home Theater Projects' started by Steve Rabbit, Feb 11, 2005.

  1. Steve Rabbit

    Steve Rabbit Agent

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    Ive got these nasty peaks at 250 Hz. So, I simply set about making a notch filter to smooth out the peak. Unfortunately, 400 Hz is rather sensitive, and I want to maximize LFE if I can. (this is the reason I havent just used a highpass filter) Using the parallel notch filter equasions, Ive come up with component values, which seem to not help 250 and cause a sinkhole at 400.

    trying to reason with it and try various inductor and capacitance values, nothing seems to help, only worsen the peak. The only thing I can think of is that the resistance I need is between 3 and 6 ohms. My inductors have a combined resistance of far less than 3 ohms. is this what is causing my filter to fail? If so, what cna I do? eliminating all resistors from the filter still gives me about an ohm and a half resistance in the filter due to component DCR, and I cant increase resistance by adding resistors!

    adding resistors in series with the inductors within the notch but not in parallel does nothing constructive.

    What can I do?
     
  2. Michael R Price

    Michael R Price Screenwriter

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    Steve, what's the impedance of the driver you are trying to equalize? Or are you building a line level filter? Do you the anomalies aren't caused by something like floor bounce?
     
  3. Steve Rabbit

    Steve Rabbit Agent

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    I just realized an hour after I posted this I didnt know the source of the anomaly. Its a passive filter I am trying to build, But I can't be sure of what is causing it.

    the speaker as it is right now sits only five or six inches above a hard surface. It could be floor bounce, but not from the surface its directly on. I realized immediately it could be enclosure based. How embarasing.

    But I will try both ideasout, see if either one, eliminating floor bounce and increasing enclosure size helps.

    Now, to eliminate floor bounce, if I merely increase the distance from the driver to the floor to about four feet, will that do it? and it shouldnt matter there are surfaces behind the speaker, objects like this? I have the test setup on a desk right now, and I could turn the spekaer around so the desk surface sits behind the speaker. should this be adequate to test agasint floor bounce?
     
  4. Steve Rabbit

    Steve Rabbit Agent

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    wierd, with the smaller enclosure, nothing helped. Increasing enclosure size didnt help at all either, but the notch filter actually worked when I used this enclosure. I'm still kinda scratching my head.
     

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